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Tue, 20 Apr 2021 20:42:01 -0700 (PDT) MIME-Version: 1.0 References: <20210415084005.25049-1-songmuchun@bytedance.com> <20210415084005.25049-9-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Wed, 21 Apr 2021 11:41:24 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v20 8/9] mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled To: Oscar Salvador Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , Ingo Molnar , bp@alien8.de, X86 ML , hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , Alexander Viro , Andrew Morton , paulmck@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Joao Martins , Xiongchun duan , fam.zheng@bytedance.com, linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3D1782000250 X-Stat-Signature: s91jzcift6udnkd6bbw6qgq63zj6hhfp Received-SPF: none (bytedance.com>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=mail-pf1-f169.google.com; client-ip=209.85.210.169 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618976525-960434 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 20, 2021 at 6:35 PM Oscar Salvador wrote: > > On Thu, Apr 15, 2021 at 04:40:04PM +0800, Muchun Song wrote: > > bool mhp_supports_memmap_on_memory(unsigned long size) > > { > > + bool supported; > > unsigned long nr_vmemmap_pages = size / PAGE_SIZE; > > unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page); > > unsigned long remaining_size = size - vmemmap_size; > > @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size) > > * altmap as an alternative source of memory, and we do not exactly > > * populate a single PMD. > > */ > > - return memmap_on_memory && > > - IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > > - size == memory_block_size_bytes() && > > - IS_ALIGNED(vmemmap_size, PMD_SIZE) && > > - IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > > + supported = memmap_on_memory && > > + IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > > + size == memory_block_size_bytes() && > > + IS_ALIGNED(vmemmap_size, PMD_SIZE) && > > + IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > > + > > + if (supported && is_hugetlb_free_vmemmap_enabled()) { > > + pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n"); > > + supported = false; > > + } > > I would not print anything and rather have > > return memmap_on_memory && > !is_hugetlb_free_vmemmap_enabled && > IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > size == memory_block_size_bytes() && > IS_ALIGNED(vmemmap_size, PMD_SIZE) && > IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); OK. Will do. > > Documentation/admin-guide/kernel-parameters.txt already provides an > explanation on memory_hotplug.memmap_on_memory parameter that states > that the feature cannot be enabled when using hugetlb-vmemmap > optimization. > > Users can always check whether the feature is enabled via > /sys/modules/memory_hotplug/parameters/memmap_on_memory. If memory_hotplug.memmap_on_memory is enabled $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory $ Y If memory_hotplug.memmap_on_memory is disabled $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory $ N > > Also, I did not check if it is, but if not, the fact about hugetlb-vmemmmap vs > hotplug-vmemmap should also be called out in the hugetlb-vmemmap kernel > parameter. Make sense. I will update the doc. Thanks. > > Thanks > > -- > Oscar Salvador > SUSE L3